1. Field of Invention
The present invention relates to method and apparatus for tracking the sun for use in focusing solar collectors having one or more linear focusing means, such as cylindrical parabolic or semiparabolic mirrors and linear lenses, regular or Fresnel type.
2. Brief Description of the Prior Art
There are three conventional ways of tracking the sun that are used in solar collectors with linear focusing means, such as cylindrical parabolic or semiparabolic mirrors and linear lenses. The first method is referred to as full tracking and involves two motions -- the rotation of a vertical shaft and the tilting of the collector around a horizontal axis. The second method may be referred to as the East-West rotational tracking. In this method, the long axis of the solar collector is located North to South and tilted at an angle so that the long axis is at right angles to the rays from the rising sun, and the front plane of the collector is faced toward the sun. As the sun moves across the sky, the collector is rotated around a central shaft parallel to the long axis so that the front plane of the collector is always at right angles to the sun. As the season changes, the long axis of the collector is shifted daily or weekly so that the long axis is always at right angles to the rising sun. The third method may be referred to as the North-South rotational tracking. In this method, the long axis of the collector is located horizontally East to West and is rotated North to South so that the focus of the collector coincides with the receiver throughout its length.
It is noted that in these conventional methods of tracking, the front plane of the solar collector does not remain on the same plane. A norm to the front plane changes both its altitude angle relative to the horizontal plane and its azimuth angle relative to due south. A characteristic feature of the tracking method of the present invention is that the front plane of the collector remains on the same plane.